Beamforming Design For Intelligent Reflecting Surface Aided Full Duplex Communication

Intelligent reflecting surface(IRS)is composed of a large number of low-cost passive components,which has abundant applications in future wireless networks by smartly reconfiguring the wireless channel for performance enhancement.Compared with the existing relay communication technology,IRS can reduce the power consumption of the communication system due to use of the passive array.So far,the IRS-assisted half duplex(HD)communication system has been intensively studied.In order to further improve the spectral efficiency,it is of necessity to study the application of IRS in the full-duplex(FD)communication system.In addition,due to the limitation of hardware implementation,the hardware impairment(HWI)in the transceiver cannot be ignored,thus it is important to discuss the beamforming design in the presence of HWI.This thesis focuses on the IRS-assisted multi-antenna wireless communication system,and improves the transmission performance of the system by jointly optimizing the transmit beamforming and the IRS reflection beamforming.Firstly,this thesis considers an IRS-aided point-to-point multiple input single output(MISO)HD communication system.The goal is to maximize the received signal power by jointly optimizing the transmit beamforming at the base station(BS)and the reflection beamforming at the IRS.The beamforming designs based on the semidefinite relaxation(SDR)and the minorization maximization(MM)techniques are given,and the two algorithms are compared in terms of performance and complexity.Compared with the SDR algorithm,the MM algorithm can significantly reduce the complexity with a relatively small performance loss.Secondly,concerning an IRS-aided FD communication system,the thesis maximizes the sum rate of bidirectional transmissions by jointly optimizing the transmit beamforming and the IRS reflection beamforming.A fast converging alternating algorithm is developed to tackle this problem.In each iteration of the proposed algorithm,the solutions to the transmit beamforming and the IRS reflect beamforming are obtained in a semiclosed form and a closed form,respectively.Compared with an existing method based on the ArimotoBlahut algorithm,the proposed method achieves almost the same performance while enjoying much faster convergence and lower computational complexity.Finally,the IRS-aided FD communication system in presence of the hardware impairment is further considered.The difference from the aforementioned work is that the signal distortion caused by hardware impairments is considered in the optimization of transmit beamforming and IRS reflection beamforming.We solve the corresponding transmission rate maximization problem by employing the MM algorithm.Simulation results show that the proposed algorithm can effectively improve the robustness of IRS-assisted FD communication against the hardware impairment.